1. Field of the Invention
The present invention relates to screen printing machines and, more particularly, to screen printing machines of the type which employ a plurality of article supports, e.g pallets or vacuum tables, for carrying articles to be printed, the article supports being displaceable around an endless path in succession through a plurality of printing stations each provided with a printing head.
2. Description of the Related Art
It has previously been known to provide a screen printing machine of the above-mentioned type having an endless chain for pulling the article supports around the endless path. Since it is important to ensure that the articles to be printed, which are carried on the article supports, are accurately located in position at the printing stations beneath the printing heads, locating devices have been provided at the printing stations for engaging and accurately positioning the vacuum tables. One such screen printing machine is disclosed in my co-pending U.S. patent application Ser. No. 08/939,497, filed Sep. 29, 1997, the disclosure of which is incorporated herein by reference.
However, it is a substantial disadvantage of chain-driven printing machines that the drive chain, over the course of time, tends to stretch, causing inaccuracy and possible disruption of the printing process.
It is also well known in the art to employ vacuum tables for supporting paper, plastic and other articles, known as flat stock, as the vacuum tables are advanced from station to station around an endless path.
It is an object of the present invention to provide a printing machine having a novel and improved mechanism for displacing the article supports for the articles to be printed to successive printing stations.